Underground shelter has plywood as door over opening under tool shed. How to slide plywood off of opening with motor?

I have hand dug a "bomb shelter"/ multi-use "room" under my tool shop (outdoor building). This has taken me about three years, and hundreds of buckets of dirt up the ladder! It's 12 feet deep, and currently, 6 ft high, by 5 ft wide by 5 ft wide. In the middle of the floor of the tool shop, I have cut out a piece of the floor which is on hinges, and can be opened and closed as needed. A carpet covers this when not necessary to access the shelter. Nobody knows about it but me at this point. About a foot down below that, I have created a "false" top to the opening, which is just a sheet of plywood covered with dirt, which makes it look as if it is just the ground underneath the building. Currently, I am manually sliding the plywood off of the opening, which reveals the ladder down, and lights and door into the "room". What I need help with is motorizing this process. I would like to open the hinged plywood floor (manually), see just the "ground", and then somehow, activate a motor to slide the plywood off of the opening. (The way it is now, if anyone does discover the hinged opening under the carpet, all they will see if they open it is what just looks like the ground under the building.) The "false" ground/ door to the shelter opens about 40 inches, which is room enough for anyone to get onto the ladder and go down. I have explored various options, such as linear actuators, motors and pulley's, etc, but I'm stuck. I plan to make a track for the plywood to slide back and forth in. I need to be able to slide open the "door" from the top, while up in the building (motorized), and then be able to close it when down in the "shelter". Do they make actuators with that length of throw, and if so, aren't they very expensive? I've also explored the idea of mounting a nut on the board, using threaded rod attached to a motor, and somehow open it that way. I'm not sure how much the plywood weighs with the dirt on it. Thanks so much for any help and ideas. I plan to submit pictures as I can. P.S.-Not that important just yet, but once I have the motorized opening figured out, I want to either switch it on with possibly entering a code on a keypad, or somehow a "hidden" switch, like what they did in "Batman"(TV Series), or use something in the shop that looks like one thing, but would actually trigger the motor. Thanks!!

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rickharris5 years ago
1. i trust you have supported the sides of the pit more than adequately being buried alive isn't going to be funny,

2. I hope you have some kind of drainage as your pit will act as a sump to local ground water.

3. You should be able to install 2 wooden rails and a motor to pull the trap door aside using a continuous length of chain or rope.

You will need to be able to reverse the motor to close again so will need some form of H bridge - the relay option is most likely the easiest for you.

You WILL need, as Re-design says, a fail safe manual method of opening this should power or mechanics fail "no one knows where this is" is a recipe for a slow death should you get trapped down there.

stevecinstrfme (author)  rickharris5 years ago
Thanks for your answer. I've tried to attach an image of what I have done. This is a very crude attempt at trying to show this. I don't yet have the necessary software to do a better one. New to posting questions, comments, images, etc. on here. Appreciate your patience.

1. The roof part of the "room" is supported via 4 x 4 posts and plywood. I haven't supported the sides as of yet. I plan to. The dirt is hard, compacted red clay with limestone and quartz (NC). Any suggestions on supporting it. I have thought about using rebar and cinder blocks.

2. I haven't had any problem with water yet. It's actually kind of weird. When I first started digging, and down to about 5 feet or so, I would go out and find the hole with a lot of water in it after a heavy rain. and would have to wait for it to drain. But since going deeper, and finally to my final depth of 12 ft, there hasn't been any standing water in it after rain, even heavy day long rain. Don't know why. As I stated in my question, the hole is under the middle of my outdoor building. I have wondered though, if I ever do have a problem, how to get the water out of there. The word "drain" seems to imply to me to make the water go down. How do I make it go down? Alternatively, I guess I could pump it up out of there using a sump pump that could lift water that far, (12 ft), and a piping system.

3. Not sure I understand the "2 wooden rails" idea. I appreciate your diagram and see how that would work, but I can't picture in my head how to apply your idea of the 2 wooden rails. Also, any suggestion on a motor? I have a few AC motors laying around that I think my grandfather had gotten out of textile machinery. The rpm on these are very high. Don't think these would be feasible for this, and don't really want to try to figure out how to reduce it's speed. Just a reminder, the plywood weighs, well, whatever a piece 30 in wide by 50 in long by 3/8 in thick would weigh, and then the little bit of dirt on top of it that makes it look like the ground under the building. Thanks!

Thanks to anyone for suggestions on fail safes, and letting someone in on my little endeavor. Definitely plan to do that! The thought of dying a slow, agonizing, painful death without anyone knowing where I am frightens the heck out of me!
Underground Room.jpg
Once you put the plywood on wheels the weight won't matter so much if the wheels have a flat surface to run on (the rails)

The motor needs to be a slow output so you either need to find one with a gear box or use pulleys and belts or gears to slow things down.

Wooden pulleys would do for this and are easily made.

rail.jpg
As for shoring the sides up I am not a civil engineer so I leave that to those with qualifications. BUT it needs doing no matter what type of soil your in.

As for the drainage, you may be lucky and have dug through to a permeable layer - sand or gravel so the water is falling through to find a lower level. usually basements have a sump and a pump to drain the sump when it gets full.

In general deep hols in the ground get water!
stevecinstrfme (author)  stevecinstrfme5 years ago
Attempt at bigger image.
Underground Room 2.jpg
Added picture
trap.jpg
Re-design5 years ago
It's too late right now for me to work on the problem but two things are really screaming at me to mention.

First thing - how ever you make this work BE ABSOLUTELY CERTAIN that you have a fail safe mechanism so that if the power goes out or your motor shorts out while you are in this room that you can get the door open manually.  This is incredibly dangerous if you can't open the door manually.

Second thing - someone trusted should know about this room and how to open it up if they don't hear from you for a few days.  Picture this, you get down there and have an appendicitis attack and can't get to the door to get out -  who you gonna call?